1. Field of The Invention
This invention relates to apparatus for selectively adjusting the timing of a diesel engine, and to an associated method of timing of a diesel engine.
2. Description of The Related Art
In the operation and maintenance of diesel engine power systems, it generally is very difficult to adjust the timing of the engine. Such difficulty is associated with the complex, labor-intensive, time-consuming, and resultingly costly character of the conventional methods employed for selectively adjusting the timing of diesel engines.
Taking as an example the MERCEDES 240D automotive diesel engine, the timing procedure for this engine in accordance with factory specifications may cost on the order of $250, at current prices. This high cost results from the fact that a very skilled and experienced diesel injection mechanic is required to do such work, and the fact that even when done by a competent mechanic, this work is complex and requires a substantial time to complete.
Typically, then, the adjustment of injection pump timing on diesel engines involves numerous and complicated procedures, which the majority of mechanics cannot do, since they lack the specialized equipment and training required therefor.
U.S. Pat. No. 4,441,021 to G. E. Olson et al, discloses a luminosity probe for a diesel engine timing apparatus. The disclosed probe comprises two telescopingly engaged sections, including a first portion which is exteriorly threaded for mounting in place of the glow plug in a selected diesel engine cylinder. A second portion of the probe, proximal to the first portion, contains a phototransistor located rearwardly of a light pipe in the first portion. This light pipe directs light from the combustion in the cylinder, to the phototransistor. The resulting electrical signal from the phototransistor then is carried via a cable to signal processing circuitry.
The foregoing luminosity probe is used in combination with a magnetic sensing device, located in effective relation to a moving engine part such as a notch in the harmonic balancer. The notch passes the sensing device a known number of degrees of engine and crankshaft rotation after the piston in the cylinder containing the luminosity probe has reached its top-dead-center position. The magnetic sensing device generates an electrical signal when the notch passes, and this signal is processed in associated circuitry. The processed signals from the magnetic probe and the luminosity probe then are passed to a degree meter, and the service person adjusts the fuel injection pump, so that the degrees displayed on the meter match the degrees specified by the engine manufacturer for a specific engine speed.
Related to the foregoing patent is U.S. Pat. No. 4,373,384 to G. E. Olson et al, describing circuitry which may be employed in a luminosity probe/magnetic probe timing system. Such circuitry includes a timer, for producing a recurring timer signal commencing with the electrical signal recurrently produced by the phototransistor, but with the timer signal having a substantially greater duration. A first pulse generator is responsive to the leading edge of the timer signal, and produces a train of first pulses each having a duration substantially shorter than the timer signal duration.
The second recurring electrical signal produced by the magnetic probe is passed to a second pulse generator responsive to the leading edge of the magnetic probe signal, to produce a train of second pulses. Circuitry is coupled to the first and second pulse generators, and is responsive to each first pulse, to start an output pulse, and to each second pulse, to terminate the output pulse. Display means are provided to display information corresponding to the duration of the output pulses, with an offset voltage being applied to the display means, to compensate for delay in the system relative to the actual top-dead-center event.
The timing adjustment apparatus disclosed in the aforementioned Olson et al patents requires two separate probe assemblies, viz., a luminosity probe comprising a phototransistor, and a magnetic probe. Although the luminosity probe is adapted for mounting in the glow plug opening of the diesel engine, and thus can be adapted to any diesel engine for which the exterior threading of the luminosity probe is appropriately sized, the majority of diesel engines do not have places or suitable structure for connecting the magnetic probe in the manner taught by these patents. Accordingly, the majority of diesel engines would have to modified to accommodate the magnetic probe disclosed in the Olson et al patents, since engine pump timing adjustment could not otherwise be achieved with the Olson et al apparatus.
Further, it is apparent that the Olson et al apparatus is complex, representing a specialized optical/magnetic timing system characterized by its own complicated specifications for proper operation.
Accordingly, it is an object of the present invention to provide a diesel engine timing adjustment apparatus and associated pump timing adjustment method which are simple in character, low in cost, and easy to employ.
It is another object of the invention to provide a diesel engine timing apparatus and method of such type, which may be employed with a conventional strobe-type timing light, e.g., of the hand-held gun type which is used for timing adjustment of gasoline-powered engines.
Other objects and advantages of the invention will be more fully apparent from the ensuing disclosure and appended claims.